How long will it take the Fukushima reactors to cool?

As I understand it, the reactors at the Fukushima plant "scrammed" just after the quake - the control rods were inserted, halting the nuclear reaction. What is happening now is from residual radiation and heat, but isn't the eventual goal to cool the reactor to the point where than can be "de-fuled" and decommissioned (since the salt water bath effectively ruined them)? If so, approximately how long are the workers going to have to struggle to cool the reactors?